This invention relates generally to sprinkler systems and more particularly to water driven reciprocating lawn sprinklers.
Sprinklers have been used for many years to provide enough moisture upon a surface, such as a lawn or garden, to ensure that plants growing on such surface have sufficient irrigation to support healthy growth and prevent disease or even dying. In recent years, moveable above-ground oscillating sprinklers, such as U.S. Pat. Nos. 3,332,624, 4,721,248 and 4,568,023 have been developed to provide a more uniform spray pattern over a more or less rectangular area. Such oscillating sprinklers are usually driven by a "water motor" or the like, such as is disclosed in U.S. Pat. Nos. 4,417,691 or 5,052,621 which conventionally moves the spray nozzle to point in a different direction over the spray cycle period. This allows even coverage because the water droplets impact the ground uniformly as the sprinkler oscillates.
FIG. 1 shows a conventional oscillating sprinkler at 10. Oscillating sprinkler 10 includes an elongate hollow tube 12 having a plurality of apertures 14 located along its length through which water is forced outward under pressure. At an interface 16 located at one end of tube 12, a water source, such as hose 18, is connected. Interface 16 includes water driven gearing means (not shown) for rotating tube 12 along a longitudinal axis. Finally, sprinkler 10 includes frame 20 to provide stability to the structure on which tube 12 and interface 16 are mounted. As a result of water pressure supplied through hose 18 to interface 16, the gearing means are turned, thereby oscillating tube 12 through a predetermined arc and thus dispersing water, as shown in FIG. 2, in a rectangular pattern centered about sprinkler 10.
FIG. 2 includes a diagram showing the water dispersal characteristics of oscillating sprinkler 10. The maximum distance at which water may be dispersed from the oscillating sprinkler is shown as D and is dependant upon the water pressure, the size of apertures 14, and the topography of the surface to be watered. On fiat surfaces, oscillating sprinklers have the advantage of dispersing water evenly throughout an area, as illustrated in the FIG. 2C graph showing the amount of water dispersed as a function of distance from the sprinkler. Note that water dispersal is fairly uniform across the entire watering range D.
Another type of lawn irrigating sprinkler is the fixed, in-ground system comprising a number of sprinkler heads coupled to an underground piping system. FIG. 3 shows a conventional sprinkler head 30 used with in-ground sprinkler systems. Sprinkler 30 comprises a housing 32 having a female pipe thread 34 located at one end of the housing and a water outlet 36 located at the opposite end. Housing 32 is generally made of a hard plastic material that resists wear and is immune to rust. Pipe thread 34 is conventionally sized to screw onto a standard pipe fitting on most in-ground sprinkler systems. Water supplied to housing 32 through female thread 34 is shunted to the outlet 36 where it contacts deflector 38 and is dispersed radially from the sprinkler head.
Current in-ground sprinkler systems rely on a constant water flow at each sprinkler head. The flow can be adjusted at the sprinkler head and at the valve to the sprinkler group. It is normally adjusted once during sprinkler installation, allowing water to reach vegetation while avoiding things that should remain dry (fences, windows, etc).
FIG. 4 shows the dispersal of water from sprinkler 30. The maximum distance at which water may be dispersed from sprinkler 30 is shown as radius R and is dependant, like the oscillating sprinkler, upon the water pressure, the size of outlet 36, and the topography of the surface to be watered. Because the pressure and flow of water through the outlet is constant, however, most of the water is dispersed a predominantly constant distance from the sprinkler head. FIG. 4C includes a graph showing the uneven radial dispersal of water from the sprinkler head.
Current automated and manual in-ground sprinkler systems rely upon overlapping spray patterns from a series of sprinkler heads in order to assure coverage of an area being watered. Spray patterns typically cover a full or partial circle. The full/partial circle spray pattern is created by one or more water outlets on the sprinkler head. Each water outlet shapes and deflects water in a specific direction, normally at an upward angle. Spray patterns larger than a half circle are usually produced by a sprinkler head with two water outlets--one for each half of the pattern.
When planning a sprinkler system, the radius of the spray pattern is determined for purposes of spacing the individual sprinklers. The sprinklers are typically separated by a distance equal to this radius in order to prevent unirrigated spots from existing. Because the spray from a sprinkler is normally up and away from the sprinkler at a constant flow rate, unlike the oscillating sprinkler shown in FIG. 1, a poorly irrigated area will exist near the sprinkler head unless the overlapping spray of another sprinkler can reach the "dry" area. The water coverage from a single conventional in-ground sprinkler is shown in FIG. 4. The collision of airborne drops of water from one sprinkler with drops from another sprinkler helps to assure complete coverage of the area being watered.
FIG. 5A shows a typical sprinkler configuration for a square section of grass. A full circle sprinkler head, such as sprinkler head 50, is located at the center of the square. Sprinkler 50 disperses water out to a radius, shown in dashed lines, sufficient to reach a boundary of the square section. A half-circle sprinkler head, such as sprinkler head 52, is placed at the midpoints of each of the square sides of the lawn. Sprinkler 52 disperses water in a 180 degree arc out to a radius shown by the dot-dashed line. Finally, a quarter circle sprinkler head, such as sprinkler head 54, is placed at each of the corners of the lawn to irrigate out to a radius shown by the 90 degree arc dotted lines.
Current sprinkler systems are adequate for irrigating a fiat area when the sprinkler head spacing described above is used. When the lawn area is not fiat or obstacles exist (tree roots, etc.) interfering with the sprinkler head spacing needed to create overlapping spray, a portion of the lawn will not receive adequate irrigation. This will cause a "dry patch" to exist on the lawn.
As a result of the necessity of overlapping spray patterns for uniform irrigation, more sprinkler heads are required. Additionally, placement of each sprinkler head is critical to reaching all portions of the lawn due to the inherent irregular watering patterns of conventional inground sprinkler heads.
Accordingly, a need remains for a compact sprinkler device which combines the ability to uniformly water an area as with an oscillating sprinkler, yet be compatible with existing in-ground sprinkler systems.